1. Field
The present invention relates generally to electrostatic discharge protection. More specifically, the present invention relates to systems, devices, and methods for electrostatic discharge protection of low-noise amplifier cascode devices.
2. Background
Amplifiers are commonly used in various electronics devices to provide signal amplification. Different types of amplifiers are available for different uses. For example, a wireless communication device such as a cellular phone may include a transmitter and a receiver for bi-directional communication. The receiver may utilize a low noise amplifier (LNA), the transmitter may utilize a power amplifier (PA), and the receiver and transmitter may utilize variable gain amplifiers (VGAs).
Amplifiers may be fabricated with various integrated circuit (IC) processes. Sub-micron complementary metal oxide semiconductor (CMOS) fabrication processes are commonly used for radio frequency (RF) circuits in wireless devices and other electronics devices in order to reduce cost and improve integration. However, transistors fabricated with sub-micron CMOS processes typically have small physical dimensions and are more susceptible to stress and possibly failure due to electro-static discharge (ESD). ESD is a sudden large and momentary electrical charge that may come from static electricity and/or other sources. It is desirable to effectively combat ESD while minimally affecting performance.
In a common-source cascode LNA, with an inductive load, a load tuning capacitor may exist between an output of the LNA output and a ground node. Typically, a gate of a cascode device and a supply voltage are closely coupled to the ground node through bypass capacitors. During an ESD event at an input of the LNA, due to LC resonance at the LNA output, a large voltage potential can develop between the LNA output and the gate of a cascode device, potentially rupturing the gate-drain junction of the cascode device. In an integrated receiver, the LNA output may be an internal node, which couples to a down-converter. In this case, typically, there is no ESD protection for the cascode device and, therefore, the LNA output swing may damage the cascode device, even though the transconductance transistor is undamaged.
Hence, ESD protection of LNA cascode devices is desirable. More specifically, a need exists for systems, devices, and methods for protecting LNA cascode transistor against ESD.